Prenuclear minitubers of potato (Solanum tuberosum L.) are the source material used to produce field-grown seed potatoes. Seed potatoes are in turn planted by commercial growers to produce potatoes ...for fresh packing and processing. Arbuscular mycorrhizae (AM) have been demonstrated to increase yield in low-input systems. This study was conducted to determine whether and how a commercial AM inoculum influences prenuclear minituber production under high-input commercial conditions. A peat-based medium containing the mycorrhizal fungus Glomus intraradix was tested in a commercial minituber greenhouse production facility. This medium increased yields of the most valuable sizes of prenuclear minitubers by 84%, and increased total prenuclear minituber yield by 49% when compared with conventional peat-vermiculite media under commercial growing conditions. Potato plants grown in this mycorrhizal medium had more uniform stolon development, as well as stolons 39% longer than plants grown in the conventional medium. These yield increases and morphological changes occur in the presence of very low levels of mycorrhizal colonization, and there was no evidence of the enhanced plant P nutrition generally associated with mycorrhizal symbiosis. These effects may indicate the presence of a hormonally mediated plant response to the mycorrhizae that results in more uniform stolon growth and an increase in tuber initiation
Orchard floor management impacts soil conditions and thus tree performance. This research was initiated to investigate the effects of alternative orchard floor management systems compatible with ...organic production on soil parameters using the “Pacific Gala” apple cultivar (
Malus
×
domestica
Borkh.) on three rootstocks of varying vigor. Alfalfa hay mulch, propane flame burner, and Swiss sandwich system (combination of resident vegetation and tilled strips) were compared from 2001 to 2005. These treatments were applied to tree rows which provided different vegetation-free areas. Contrasting additions of organic matter were evaluated for their effect on soil organic matter (SOM), C content, nitrate and ammonium availability, moisture, and soil food web through nematode populations. Laboratory incubations to determine C and N mineralization potentials were performed. During this time period, SOM increased under the mulched soil and slightly less under the Swiss sandwich system (SSS) but in this last case without external inputs. Carbon and N pools were not impacted by flame burning (FL) but were enhanced by alfalfa hay mulch (MU) and to a lesser extent by SSS. Nitrate-N content in soil under MU increased between five and ten times compared to SSS and FL. Total number of nematodes was higher for SSS and MU compared with FL treatment; however, SSS had the most structured soil food web, an important sustainability trait, while MU had the least.
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